This invention relates to LED lamps, and in particular to a method of forming a core for an LED lamp, as well as the lamp itself.
Incandescent lamps are slowly being replaced with more modern lamps, including LED lamps. Low intensity LED lamps can provide efficient light without the need for a large heat sink, but as luminosity increases, providing a practical lamp becomes more difficult because a large heat sink is needed to remove heat, not only affecting the aesthetics of the lamp, but also blocking some of the emitted light.
LED lamps are self contained. The power supply for driving the lamps, as well all circuitry, is located within the lamp. U.S. patent application Ser. No. 12/826,774, filed Jun. 30, 2010, the disclosure of which is incorporated herein by reference, discloses an LED lamp replacement for low power incandescent lamps. It describes an LED lamp that allows light to radiate in a full 360° view angle and maintains the look of an incandescent filament.
Higher intensity LED lamps require dissipation of heat, normally with heat sinks of various types of thermally conductive material. The heat sinks, however, tend to obstruct the light and create dark bands. It is therefore necessary to mount LEDs in a manner that allows light to radiate in all directions, while still dissipating heat. In incorporated application Ser. No. 12/826,774, because of the low power, heat is dissipated through a multi-layered printed circuit board and screw-type lamp base. That is sufficient to keep the LED junction temperature under the maximum rated value set by the manufacturer. However, increasing power requires an external sink for dissipating heat which cannot be adequately channeled through the printed circuit board and lamp base.
For dissipating heat in higher intensity LED lamps, the individual LEDs are mounted on a thermally conductive medium, such as an aluminum plate. However, mounting LEDs on a plate of even nominal thickness will reduce the view angle of the emitted light, resulting in a noticeable band of lower intensity light when projected on a nearby surface.